I'm not entirely sure what you're asking but your XFX will support DDR2 800 RAM as that's in its spec. You may also see it referred to as DDR2 6400. If you're unsure what memory ratings mean just have a quick look at THG. And you can probably OC ballistix to run at 1066 but bear in mind the XFX doesn't have passive cooling so you'll have 2 fans cooliing the MB, then fans for the CPU, PSU and chassis fans.
I'm thinking about getting the XFX for a build myself but all those fans must get annoying!